You cannot select more than 25 topics Topics must start with a letter or number, can include dashes ('-') and can be up to 35 characters long.
parallel-library/cps/static/js/io.js

484 lines
15 KiB
JavaScript

/*
* io.js
*
* Provides readers for bit/byte streams (reading) and a byte buffer (writing).
*
* Licensed under the MIT License
*
* Copyright(c) 2011 Google Inc.
* Copyright(c) 2011 antimatter15
*/
/* global bitjs, Uint8Array */
var bitjs = bitjs || {};
bitjs.io = bitjs.io || {};
(function() {
// mask for getting the Nth bit (zero-based)
bitjs.BIT = [ 0x01, 0x02, 0x04, 0x08,
0x10, 0x20, 0x40, 0x80,
0x100, 0x200, 0x400, 0x800,
0x1000, 0x2000, 0x4000, 0x8000];
// mask for getting N number of bits (0-8)
var BITMASK = [0, 0x01, 0x03, 0x07, 0x0F, 0x1F, 0x3F, 0x7F, 0xFF ];
/**
* This bit stream peeks and consumes bits out of a binary stream.
*
* @param {ArrayBuffer} ab An ArrayBuffer object or a Uint8Array.
* @param {boolean} rtl Whether the stream reads bits from the byte starting
* from bit 7 to 0 (true) or bit 0 to 7 (false).
* @param {Number} optOffset The offset into the ArrayBuffer
* @param {Number} optLength The length of this BitStream
*/
bitjs.io.BitStream = function(ab, rtl, optOffset, optLength) {
if (!ab || !ab.toString || ab.toString() !== "[object ArrayBuffer]") {
throw "Error! BitArray constructed with an invalid ArrayBuffer object";
}
var offset = optOffset || 0;
var length = optLength || ab.byteLength;
this.bytes = new Uint8Array(ab, offset, length);
this.bytePtr = 0; // tracks which byte we are on
this.bitPtr = 0; // tracks which bit we are on (can have values 0 through 7)
this.peekBits = rtl ? this.peekBitsRtl : this.peekBitsLtr;
};
/**
* byte0 byte1 byte2 byte3
* 7......0 | 7......0 | 7......0 | 7......0
*
* The bit pointer starts at bit0 of byte0 and moves left until it reaches
* bit7 of byte0, then jumps to bit0 of byte1, etc.
* @param {number} n The number of bits to peek.
* @param {boolean=} movePointers Whether to move the pointer, defaults false.
* @return {number} The peeked bits, as an unsigned number.
*/
bitjs.io.BitStream.prototype.peekBitsLtr = function(n, movePointers) {
if (n <= 0 || typeof n !== typeof 1) {
return 0;
}
movePointers = movePointers || false;
var bytePtr = this.bytePtr;
var bitPtr = this.bitPtr;
var result = 0;
var bitsIn = 0;
var bytes = this.bytes;
// keep going until we have no more bits left to peek at
// TODO: Consider putting all bits from bytes we will need into a variable and then
// shifting/masking it to just extract the bits we want.
// This could be considerably faster when reading more than 3 or 4 bits at a time.
while (n > 0) {
if (bytePtr >= bytes.length) {
throw "Error! Overflowed the bit stream! n=" + n + ", bytePtr=" + bytePtr + ", bytes.length=" +
bytes.length + ", bitPtr=" + bitPtr;
}
var numBitsLeftInThisByte = (8 - bitPtr);
var mask;
if (n >= numBitsLeftInThisByte) {
mask = (BITMASK[numBitsLeftInThisByte] << bitPtr);
result |= (((bytes[bytePtr] & mask) >> bitPtr) << bitsIn);
bytePtr++;
bitPtr = 0;
bitsIn += numBitsLeftInThisByte;
n -= numBitsLeftInThisByte;
} else {
mask = (BITMASK[n] << bitPtr);
result |= (((bytes[bytePtr] & mask) >> bitPtr) << bitsIn);
bitPtr += n;
bitsIn += n;
n = 0;
}
}
if (movePointers) {
this.bitPtr = bitPtr;
this.bytePtr = bytePtr;
}
return result;
};
/**
* byte0 byte1 byte2 byte3
* 7......0 | 7......0 | 7......0 | 7......0
*
* The bit pointer starts at bit7 of byte0 and moves right until it reaches
* bit0 of byte0, then goes to bit7 of byte1, etc.
* @param {number} n The number of bits to peek.
* @param {boolean=} movePointers Whether to move the pointer, defaults false.
* @return {number} The peeked bits, as an unsigned number.
*/
bitjs.io.BitStream.prototype.peekBitsRtl = function(n, movePointers) {
if (n <= 0 || typeof n !== typeof 1) {
return 0;
}
movePointers = movePointers || false;
var bytePtr = this.bytePtr;
var bitPtr = this.bitPtr;
var result = 0;
var bytes = this.bytes;
// keep going until we have no more bits left to peek at
// TODO: Consider putting all bits from bytes we will need into a variable and then
// shifting/masking it to just extract the bits we want.
// This could be considerably faster when reading more than 3 or 4 bits at a time.
while (n > 0) {
if (bytePtr >= bytes.length) {
throw "Error! Overflowed the bit stream! n=" + n + ", bytePtr=" + bytePtr + ", bytes.length=" +
bytes.length + ", bitPtr=" + bitPtr;
// return -1;
}
var numBitsLeftInThisByte = (8 - bitPtr);
if (n >= numBitsLeftInThisByte) {
result <<= numBitsLeftInThisByte;
result |= (BITMASK[numBitsLeftInThisByte] & bytes[bytePtr]);
bytePtr++;
bitPtr = 0;
n -= numBitsLeftInThisByte;
} else {
result <<= n;
result |= ((bytes[bytePtr] & (BITMASK[n] << (8 - n - bitPtr))) >> (8 - n - bitPtr));
bitPtr += n;
n = 0;
}
}
if (movePointers) {
this.bitPtr = bitPtr;
this.bytePtr = bytePtr;
}
return result;
};
/**
* Some voodoo magic.
*/
bitjs.io.BitStream.prototype.getBits = function() {
return (((((this.bytes[this.bytePtr] & 0xff) << 16) +
((this.bytes[this.bytePtr + 1] & 0xff) << 8) +
((this.bytes[this.bytePtr + 2] & 0xff))) >>> (8 - this.bitPtr)) & 0xffff);
};
/**
* Reads n bits out of the stream, consuming them (moving the bit pointer).
* @param {number} n The number of bits to read.
* @return {number} The read bits, as an unsigned number.
*/
bitjs.io.BitStream.prototype.readBits = function(n) {
return this.peekBits(n, true);
};
/**
* This returns n bytes as a sub-array, advancing the pointer if movePointers
* is true. Only use this for uncompressed blocks as this throws away remaining
* bits in the current byte.
* @param {number} n The number of bytes to peek.
* @param {boolean=} movePointers Whether to move the pointer, defaults false.
* @return {Uint8Array} The subarray.
*/
bitjs.io.BitStream.prototype.peekBytes = function(n, movePointers) {
if (n <= 0 || typeof n !== typeof 1) {
return 0;
}
// from http://tools.ietf.org/html/rfc1951#page-11
// "Any bits of input up to the next byte boundary are ignored."
while (this.bitPtr !== 0) {
this.readBits(1);
}
movePointers = movePointers || false;
var bytePtr = this.bytePtr;
// var bitPtr = this.bitPtr;
var result = this.bytes.subarray(bytePtr, bytePtr + n);
if (movePointers) {
this.bytePtr += n;
}
return result;
};
/**
* @param {number} n The number of bytes to read.
* @return {Uint8Array} The subarray.
*/
bitjs.io.BitStream.prototype.readBytes = function(n) {
return this.peekBytes(n, true);
};
/**
* This object allows you to peek and consume bytes as numbers and strings
* out of an ArrayBuffer. In this buffer, everything must be byte-aligned.
*
* @param {ArrayBuffer} ab The ArrayBuffer object.
* @param {number=} optOffset The offset into the ArrayBuffer
* @param {number=} optLength The length of this BitStream
* @constructor
*/
bitjs.io.ByteStream = function(ab, optOffset, optLength) {
var offset = optOffset || 0;
var length = optLength || ab.byteLength;
this.bytes = new Uint8Array(ab, offset, length);
this.ptr = 0;
};
/**
* Peeks at the next n bytes as an unsigned number but does not advance the
* pointer
* TODO: This apparently cannot read more than 4 bytes as a number?
* @param {number} n The number of bytes to peek at.
* @return {number} The n bytes interpreted as an unsigned number.
*/
bitjs.io.ByteStream.prototype.peekNumber = function(n) {
// TODO: return error if n would go past the end of the stream?
if (n <= 0 || typeof n !== typeof 1) {
return -1;
}
var result = 0;
// read from last byte to first byte and roll them in
var curByte = this.ptr + n - 1;
while (curByte >= this.ptr) {
result <<= 8;
result |= this.bytes[curByte];
--curByte;
}
return result;
};
/**
* Returns the next n bytes as an unsigned number (or -1 on error)
* and advances the stream pointer n bytes.
* @param {number} n The number of bytes to read.
* @return {number} The n bytes interpreted as an unsigned number.
*/
bitjs.io.ByteStream.prototype.readNumber = function(n) {
var num = this.peekNumber( n );
this.ptr += n;
return num;
};
/**
* Returns the next n bytes as a signed number but does not advance the
* pointer.
* @param {number} n The number of bytes to read.
* @return {number} The bytes interpreted as a signed number.
*/
bitjs.io.ByteStream.prototype.peekSignedNumber = function(n) {
var num = this.peekNumber(n);
var HALF = Math.pow(2, (n * 8) - 1);
var FULL = HALF * 2;
if (num >= HALF) num -= FULL;
return num;
};
/**
* Returns the next n bytes as a signed number and advances the stream pointer.
* @param {number} n The number of bytes to read.
* @return {number} The bytes interpreted as a signed number.
*/
bitjs.io.ByteStream.prototype.readSignedNumber = function(n) {
var num = this.peekSignedNumber(n);
this.ptr += n;
return num;
};
/**
* This returns n bytes as a sub-array, advancing the pointer if movePointers
* is true.
* @param {number} n The number of bytes to read.
* @param {boolean} movePointers Whether to move the pointers.
* @return {Uint8Array} The subarray.
*/
bitjs.io.ByteStream.prototype.peekBytes = function(n, movePointers) {
if (n <= 0 || typeof n !== typeof 1) {
return null;
}
var result = this.bytes.subarray(this.ptr, this.ptr + n);
if (movePointers) {
this.ptr += n;
}
return result;
};
/**
* Reads the next n bytes as a sub-array.
* @param {number} n The number of bytes to read.
* @return {Uint8Array} The subarray.
*/
bitjs.io.ByteStream.prototype.readBytes = function(n) {
return this.peekBytes(n, true);
};
/**
* Peeks at the next n bytes as a string but does not advance the pointer.
* @param {number} n The number of bytes to peek at.
* @return {string} The next n bytes as a string.
*/
bitjs.io.ByteStream.prototype.peekString = function(n) {
if (n <= 0 || typeof n !== typeof 1) {
return "";
}
var result = "";
for (var p = this.ptr, end = this.ptr + n; p < end; ++p) {
result += String.fromCharCode(this.bytes[p]);
}
return result;
};
/**
* Returns the next n bytes as an ASCII string and advances the stream pointer
* n bytes.
* @param {number} n The number of bytes to read.
* @return {string} The next n bytes as a string.
*/
bitjs.io.ByteStream.prototype.readString = function(n) {
var strToReturn = this.peekString(n);
this.ptr += n;
return strToReturn;
};
/**
* A write-only Byte buffer which uses a Uint8 Typed Array as a backing store.
* @param {number} numBytes The number of bytes to allocate.
* @constructor
*/
bitjs.io.ByteBuffer = function(numBytes) {
if (typeof numBytes !== typeof 1 || numBytes <= 0) {
throw "Error! ByteBuffer initialized with '" + numBytes + "'";
}
this.data = new Uint8Array(numBytes);
this.ptr = 0;
};
/**
* @param {number} b The byte to insert.
*/
bitjs.io.ByteBuffer.prototype.insertByte = function(b) {
// TODO: throw if byte is invalid?
this.data[this.ptr++] = b;
};
/**
* @param {Array.<number>|Uint8Array|Int8Array} bytes The bytes to insert.
*/
bitjs.io.ByteBuffer.prototype.insertBytes = function(bytes) {
// TODO: throw if bytes is invalid?
this.data.set(bytes, this.ptr);
this.ptr += bytes.length;
};
/**
* Writes an unsigned number into the next n bytes. If the number is too large
* to fit into n bytes or is negative, an error is thrown.
* @param {number} num The unsigned number to write.
* @param {number} numBytes The number of bytes to write the number into.
*/
bitjs.io.ByteBuffer.prototype.writeNumber = function(num, numBytes) {
if (numBytes < 1) {
throw "Trying to write into too few bytes: " + numBytes;
}
if (num < 0) {
throw "Trying to write a negative number (" + num +
") as an unsigned number to an ArrayBuffer";
}
if (num > (Math.pow(2, numBytes * 8) - 1)) {
throw "Trying to write " + num + " into only " + numBytes + " bytes";
}
// Roll 8-bits at a time into an array of bytes.
var bytes = [];
while (numBytes-- > 0) {
var eightBits = num & 255;
bytes.push(eightBits);
num >>= 8;
}
this.insertBytes(bytes);
};
/**
* Writes a signed number into the next n bytes. If the number is too large
* to fit into n bytes, an error is thrown.
* @param {number} num The signed number to write.
* @param {number} numBytes The number of bytes to write the number into.
*/
bitjs.io.ByteBuffer.prototype.writeSignedNumber = function(num, numBytes) {
if (numBytes < 1) {
throw "Trying to write into too few bytes: " + numBytes;
}
var HALF = Math.pow(2, (numBytes * 8) - 1);
if (num >= HALF || num < -HALF) {
throw "Trying to write " + num + " into only " + numBytes + " bytes";
}
// Roll 8-bits at a time into an array of bytes.
var bytes = [];
while (numBytes-- > 0) {
var eightBits = num & 255;
bytes.push(eightBits);
num >>= 8;
}
this.insertBytes(bytes);
};
/**
* @param {string} str The ASCII string to write.
*/
bitjs.io.ByteBuffer.prototype.writeASCIIString = function(str) {
for (var i = 0; i < str.length; ++i) {
var curByte = str.charCodeAt(i);
if (curByte < 0 || curByte > 255) {
throw "Trying to write a non-ASCII string!";
}
this.insertByte(curByte);
}
};
})();